Slide transformer

ABSTRACT

A slide transformer has two taps on each winding of a coil wound around the magnetic path of an iron core. The taps are connected to contacts respectively and a brush is slideable across these contacts. In a transformer with a shell-type iron core, one of these taps comes out of the upper side of the iron core, the other comes out of the lower side. In a transformer with a coretype iron core, one of the taps is connected to a contact through a hole provided in the magnetic path of the iron core, and the other is connected directly to the other contact.

United States Patent Primary Examiner-Gerald Goldberg Attorney-Wenderoth, Lind & Ponack ABSTRACT: A slide transformer has two taps on each winding ofa coil wound around the magnetic path of an iron core. The taps are connected to contacts respectively and a brush is slideable across these contacts. ln a transformer with a shelltype iron core, one of these taps comes out of the upper side of the iron core, the other comes out of the lower side. In a trans former with a core-type iron core, one of the taps is connected to a contact through a hole provided in the magnetic path of the iron core, and the other is connected directly to the other PATENTEnsEmmn 3, 09,515

sum 1 0F 2 TSUNEO NAGATOSHI,

IN VENTOR BYMMIEZLWM ATTORNEY SLIDE TRANSFORMER BACKGROUND OF THE INVENTION When voltage is regulated continuously by the use of a transformer, a part of the winding is inevitably short circuited and the resultant short circuit current flows therein.

In a voltage regulator according to the prior art, the short circuit current at the brush contact is reduced by increasing the impedance of the coil circuit. To increase the impedance, a resistor, reactor, or the like Summary of the Invention.

An object of this invention is to reduce such short circuit current without using a resistor, a reactor or the like but by utilizing the magnetomotive force produced by said short circuit current.

Generally, in a shell-type iron core construction, a magnetic flux nearly equal to the flux in the central magnetic path is passed through bothsides of the magnetic path. Now, it is assumed that a turn of wire is wound on one or the other side of said magnetic path, to short circuit a part of the flux. Due to this arrangement, a short circuit current flows in the winding and, as a result the amount of the flux passing through the magnetic path differs according to the side on which it passes; the flux decreases on the side having the short-circuited winding, and increases on the other side. The flux in the central magnetic path remains unchanged.

In this manner, a part of the magnetic path is split into two in the shell-type iron core construction. If, therefore, one of the split paths is short circuited by the use of a wire, the resultant shore circuit current flows in the winding. The mag netomotive force due to this short circuit current serves to reduce the flux. When the flux is reduced, the short circuit current is accordingly reduced. The invention utilizes this principle. According to this invention, the magnetomotive force produced due to the short circuit current is utilized to reduce the magnetic flux in the magnetic path of the short-circuited coil, and thus to reduce the electromotive force of the coil whereby the short circuit current is reduced.

A further object of the present invention is to provide a slide transformer in which a metal brush is directly in contact with contacts, thereby preventing a short circuit current from being generated at the time of contact of these members without using a resistor, a reactor or the like. To this end in the slide transformer of the present invention a tap is provided on each winding and a further tap is provided for each half winding. These two taps are separated and connected to contacts respectively. A brush is provided which slides on these contacts. Thus for a shell-type iron core, a tap for each winding of the coil provided around the magnetic path in the middle comes out of the upper side of the iron core. Another tap for each half winding comes out of the lower side of the iron core. All these taps are connected to contacts respectively.

For a core type iron core, an iron core with holes for passing the wire therethrough is provided in the middle of the magnetic path of the iron core. Taps for each winding are directly connected to contacts respectively. Taps for each half winding are connected to contacts through said holes of the iron core. Accordingly the number of holes should be equal to that of the taps for each half winding. Although wires of more than two taps may pass through one hole, this requires a larger hole, so that the iron core must also be uneconomically larger sized. If all wires of the taps for each half winding are passed through one hole, such a core-type iron core cannot be distinguished from a shelltype core.

In both types of iron core, the short circuit formed by the short circuit of contacts and the brush surrounds one of the magnetic paths of the iron core which are split into two (left and right magnetic paths in the case of a shell-type, or both magnetic paths divided into two by the hole in the case of core-type) with the wire of the circuit short circuited by the brush. Accordingly, when current flow through the short circuited circuit, the magnetic flux in this circuit is reduced together with the short circuit current. However the magnetic flux of another half magnetic path increases by the amount of reduction of the aforementioned magnetic flux. Consequently in the slide transformer of the present inventions, the magnetic flux density of the iron core should be somewhat lower than its ordinary calculated valve. Further the brush should be nearly equal to the contact in width and it should not simultaneously come into contact with three contacts.

The second object of the present invention is to provide a slide transformer for a high current,'i.e. current of about several hundred amperes. In the slide transformer of the present invention, a short circuit current of not less than 50 A. should flow in order to make possible an economical design. Accordingly such a slide transformer is not suitable for a low current. The reason why a slide transformer for a high current and having an excellent characteristic can be manufactured according to the present invention is that said transformer uses a metal brush as a contact and can thus dispense with a reactor or the like. However since the present slide transformer has a number of taps and uses an iron core with holes as a core type does, the output voltage of one slide transformer is economically about 10 V.

However if the present transformer is used together with a v. or 200 v. transformer with taps a voltage regulator for a high current of ordinary voltage can be made at low cost and the voltage can be regulated as desired.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an electrical circuit diagram showing a voltage regulator using a shell-type iron core transformer, and FIG. 2 is an electrical circuit diagram showing a voltage regulator using a core-type iron core transformer. FIG. 3 is a diagram showing how the invention is applied to a circuit I00 v. or 200 v.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention employing a shell-type iron core will be more specifically explained with reference to FIG. I. The references 1 and 1 denote windings of a coil wound on a central magnetic path 2. Taps are connected to each winding of the coil its upper and lower sides. 3 and 4 are the taps for the upper winding and are connected to contacts 5 and 6 respectively. Similarly, 7, 8 and 17a are taps from the lower winding and are connected to contacts 9, l0 and 17 respectively. 11 denotes a brush in sliding and having a width no greater than two contacts with these contacts. 12 and 13 denote the two sides of the magnetic path of the iron core. [4, l5, and 16 are terminals on the input and output ends of the coil and the brush 11, respectively.

When the contact 5 is connected to the contact 9 by the brush 11, the lead wire 3, the part 1 of the winding of the coil and lead wire 7 make up a short circuit. The magnetic path 12 extends through this circuit. Therefore a short circuit current flows in the winding. Because of this short circuit current, the flux in the magnetic path 12 decreases and that in the other magnetic path 13 increases. When the contact 6 is connected to the contact 10 by the brush 11, the circuit comprising the lead wire 8, the part 1 of the winding of the coil and lead wire 4 is short circuited. As a result, the flux in the magnetic path 13 decreases and that in the other magnetic path 12 increases. In this manner, the flux decreases in either magnetic path 12 or 13 whenever the contacts are short circuited by the brush. Therefore the short circuit current is reduced.

FIG. 2 illustrates an example of a coretype iron core used for the voltage regulator. The manner in which the taps are connected to the windings of the coil is similar to treat explained in connection with the shelltype iron core construction shown in FIG. 1.

Holes 22, 23 and 24 corresponding to the number of taps 19, 18 and 20 connected to the inside of the windings of the coil are provided in the vicinity of the center of the cross section of the parts of the iron core 21. The tap lead wires 18, I9 and 20 from the inside of the windings are connected to contacts 25, 26 and 27 respectively. And extend through said holes 22, 23 and 24. By this arrangement, the magnetic path is split into two at each of the holes, and the flux is reduced due to the short circuit current. The short circuit current is accordingly reduced, as is the case with the shell-type iron core.

According to the results obtained from actual experiments, the value of the short circuit current is about 260 amperes in the conventional structure of two-terminal connecting one turn type; whereas, it is about 50 amperes in the intermediate taptype structure according to this invention.

According to this invention, two taps are connected to one winding of the coil and, accordingly, it is difficult to provide a voltage regulator in which the number of turns of the winding of the coil is large. To provide a voltage regulator applicable to a circuit of 100 v. and 200 v. it is necessary to provide an arrangement as shown in F IG. 3.

According to a conventional voltage regulation means, a transformer having taps for small voltages is connected in series to a transformer having taps for voltage several times larger than said small voltages, and the two transformers are adjusted separately by means of a switch whereby the voltages are regulated.

F IG. 3 shows a method in which a transformer of this invention is utilized in place of said transformer having small voltage taps, and another transformer having several high voltage taps is used in combination with the transformer having small voltage taps. This method permits voltage regulation for a circuit of 100 v. or 200 v. and such voltage regulation can be carried out merely by turning a handle.

Specifically, the reference 28 denotes a winding coil of this invention. Taps 29 and 30 from winding are connected to a rectifier type movable contact 32 which is mounted on an insulative disk 31. 33 denotes a winding provided with several taps across which an equal voltage is applied. Terminals 35 and 36 of a coil 34 are connected to terminals 37 and 38 of the coil 28. In other words the coil 34 serves to excite 39 and 40 are a series of pairs of fixed contacts mounted around the periphery of disk 31, to which contacts the taps of the winding 33 are connected respectively. The interval between the fixed contacts 39 and 40 is equal to that between the terminals 41 and 42 of the rectifier type movable contacts 32. When the terminals 41 and 42 of the rectifier-type movable contact 32 come in contact with the fixed contact and 40 respectively, this means that the coil 28 is connected in parallel with the portion 43 between the taps of the winding 33. In this case, no short circuit current will flow therein since the two winding have the same voltage.

The slide transfonner of this invention carries a relatively large current. Therefore it may be so arranged that flexible wire is not used for the lead wires 29 and 30 which connect tap to tap, the transformer itself having the coil 28 is made movable integrally with the rectifier type movable contact 32, and flexible wire is employed for only the lead wires 44 and 45 which connect to the winding 34. Alternatively, an arrangement such as a slipring may be employed for the same purpose.

46 and 47 denote input terminals; and 47 and 48, output terminals.

In the arrangement as described above, the voltage can be easily regulated by rotating the rectifier type movable contact 32. This arrangement makes it possible to provide the voltage regulators relatively easily, which can be applied to circuit of lOO v., 200 v. or more voltage. According to this invention, therefore, a highly efficient voltage regulator producing very little voltage drop can be provided without using a resistor, reactor or the like.

What I claim is:

l. A slide transformer comprising an iron core having a plurality of legs, a coil of windings on one leg of said core, a tap connected to the end of each winding of the coil and a tap connected to the middle of each winding of said coil, a plurality of contacts to which said taps are connected in the same order in which they are connected to said coil, respectively, at

least some of said taps extending in flux modifying relationship to at least one other leg of said core between t e windings and the contacts, and a brush slidably mounted on the contacts for electrically connecting adjacent contacts at the same time.

2. A slide transformer as claimed in claim 1 in which said core is a shell-type iron core having at least three parallel legs magnetically connected at the ends thereof, said coil is wound on the middle leg, the taps from the ends of the windings of the coil extending from one side of the iron core past one side of the core extending past the other side of the said one end leg, whereby a short circuit current in a pair of adjacent taps flows around said one end leg.

3. A slide transformer as claimed in claim I in which said core is a core type iron core having two parallel legs connected by end pieces, one of the legs and the end pieces having holes through the middle of the cross sections thereof, said coil being wound on the other leg of the core, the taps from the ends of the winding of the coil extending directly away from the other leg to the contacts, and the taps from the middle of the windings of the coil passing through the holes in the one leg and the end pieces. 

1. A slide transformer comprising an iron core having a plurality of legs, a coil of windings on one leg of said core, a tap connected to the end of each winding of the coil and a tap connected to the middle of each winding of said coil, a plurality of contacts to which said taps are connected in the same order in which they are connected to said coil, respectively, at least some of said taps extending in flux modifying relationship to at least one other leg of said core between the windings and the contacts, and a brush slidably mounted on the contacts for electrically connecting adjacent contacts at the same time.
 2. A slide transformer as claimed in claim 1 in which said core is a shell-type iron core having at least three parallel legs magnetically connected at the ends thereof, said coil is wound on the middle leg, the taps from the ends of the windings of the coil extending from one side of the iron core past one side of one of the end legs, and the taps from the other side of the core extending past the other side of the said one end leg, whereby a short circuit current in a pair of adjacent taps flows around said one end leg.
 3. A slide transformer as claimed in claim 1 in which said core is a core type iron core having two parallel legs connected by end pieces, one of the legs and the end pieces having holes through the middle of the cross sections thereof, said coil being wound on the other leg of the core, the taps from the ends of the winding of the coil extending directly away from the other leg to the contacts, and the taps from the middle of the windings of the coil passing through the holes in the one leg and the end pieces. 